Signal repeater system

ABSTRACT

The present invention concerns analog signal repeater system solutions of the general kind. It concerns in particular stability with analog signal repeater systems.

INTRODUCTION

The present invention concerns analogue signal repeater system conceptsof the general type as explained in the preamble of the appended claim1, as well as analogue signal repeater as described in appended claim.

BACKGROUND

During the last 20 years, analogue, high frequency repeaters in datacommunication systems have been neglected in favour of digital concepts.Analogue gain may be realised with analogue or digital signal processingmethods and are characterised firstly by their full or parttransparency. They offer an amplified, analogue representation of theinput signal to give a near sustained bandwidth and very low latencyeven at very large system bandwidths. Digital repeaters are nottransparent and are commonly based on just one type of modulation aswell as one type of communication protocol, which again is likely to beof proprietary character. The resulting conversion that takes placewithin them causes high supply current draws and they tend to be oflarge physical dimensions. In addition each repeater contributes to asubstantial reduction of the overall bandwidth of the system and alwaysintroduces problematic latencies that either excludes or complicatescertain modern, time critical telecommunication services. There arephysical limitations as well to which extent technologies within digitalrepeaters can be developed for large bandwidths. With knownsemiconductor types there are physical limits to how much it is possibleto reduce current consumption at high processing speeds being limited,amongst other factors, by the lower limit of transistor bias and clockfrequencies. Such concepts are likewise not inexpensive in production asfor instance due to their obligation to utilise the newest and mostexpensive technology available. Such technologies are therefore likelyto be quickly replaced by new generations leading to hi write-off costs.As a consequence, it is too expensive and impracticable to use asufficient number of such repeaters for, as an example sustaining signallevels on cables or for wireless coverage in an area where line of sightobstructions are significant. There exists therefore a great need ofnovel solutions that will give repeaters that may be utilised in greatnumbers and have low productions costs, which have small dimensions andconsume low currents. An analogue repeater system may as well be madecompatible with any existing, none proprietary communication system andmight be prepared for most future ones. Analogue repeaters do not havethe disadvantages associated with mentioned digital repeaters. It hasbeen claimed that analogue repeaters as opposed to digital repeatersaccumulate noise. These are conclusions with substantial flaws inaddition to the fact that digital repeater systems will accumulate noisethat gradually reduces symbol bandwidth in addition to the band widthreduction being caused by the latency associated with each repeater. Itis known from analogue repeaters of old times used in telephone systemsthat they were able to convey the signals across the globe. Withregenerative, super regenerative and super heterodyne analogue repeatersone may obtain regeneration of the signal which among other things isowing to averaging of noise similar to what happens when amplifiers areconnected in parallel. The accumulated, systematic noise may be reducedwith various measures. A significant number of analogue repeaters may beutilised without substantial degeneration of the signal if the repeaterdesign measures are taken. The advantage of analogue repeaters is theirsignificantly lower power consumption as compared to digital repeaters.This is particularly important when repeaters are battery powered orwill have to live off currents flowing in conductors that the repeatersare coupled loosely to, for example by inductive means.

In repeater or transponder systems as given in patent documentsNO20001057, NO20010132, NO20020112, PCT/NO01/00079, PCT/NO03/00004 it isshown how analogue repeaters and systems using analogue repeaters may berealised within none optimal cases for both wireless and wire boundconcepts or a hybrid of those. Characteristic of such sub optimal casesas when conventional solutions are not applicable, is when sufficientattenuation between input signal and output signal easily does not lenditself to be made larger than the signal gain of the repeater.Consequently it is also characteristic of such cases that there arepoints along the signal medium where analogue gain is required but whereit is impractical to insert the mentioned attenuation. Examples of thisare cable connections that cannot be broken up as in power gridnetworks. One example of wireless applications is when only one antennacan be used or when large distance in the form of a number ofwavelengths between antennas cannot be realised. Additional examples ofnone optimal cases are when isolation between input and output signal isreduced from reflections from various causes. This may be the case forwire bound and wireless systems. In wire bound systems certain controlof this may usually be exercised in wireless systems varying reflectionparameters are often a larger problem. A one port gain block that is arepeater is stabile only as long as sufficient attenuation is presentbetween the gain block or repeater and the reflection occurring in thesystem or repeater cascade. There exists therefore a need for novel,simple solutions making it more practicable to meet such challenges. Insome cases conventional concepts have applied circulators to attainattenuation of reflections and to obtain directional sensitivity.However, in large scale context this is too expensive and additionallyit is often impracticable. Even other types of directional sensitivitymay be impracticable to implement. The consequences of insufficientattenuation between input and output signal in signal repetition usingfrequency transposing is duplex interference.

The consequences under the mentioned, none optimal conditions as aresult of reflections or lack of attenuation may be that stabilityrequirements cannot be sustained for signal repetition within the samechannel.

When frequency transposing is applied to analogue repeater systems it isoften important that a minimum of channels are used for duplex purposesin order to acquire the largest possible efficient symbol bandwidthusing the available frequency spectrum in addition to securing channelsfor two-way communication or multiple channel systems for increasing theavailable system bandwidth. In this context it is also necessary to beable to allocate neighbouring channels as close to each other aspossible. Super regenerative frequency mixers allow very small spacingbetween input and output channel in a repeater as shown in thepublications NO20001057, NO20010132, NO20020112, PCT/NO01/00079,PCT/NO03/00004. There exists a need for novel applications that caneconomise the use of available, useful channels in such systems. This isparticularly important for modern broadband applications. It is alsoparticularly important in wireless applications where frequency banddensity is heavy. Even more important may this be in cable basedsystems, especially cables with poor high frequency characteristicswhere often just marginal frequency regions are available for the symbolbandwidth required now and in the future.

When gain is larger than 1 within the same frequency region for arepeater the stability criteria are important for utilisation of thegain. Reflections and echo from other repeaters play an important roleto achieve stability. Phase is affected by the complex impedance thatthe gain block (amplifier) looks at and by the attenuation between portsof a multiple port gain block Analogue gain has to a large extent beenabandoned in modern networks due to the difficult task of combiningstability and satisfactory gains. It is especially difficult to makesolutions that are both repeatable and possibly producible in largequantities or large systems. Directional attenuation in some form isoften the only and the best measure taken against echo and reflections.In some applications attenuation of interference of 10 to 20 dB issatisfactory, but in other applications that require good linearity aswith QAM and OFDM attenuation of 30-50 dB is necessary. For somemodulation types problems with frequency beating can occur even withrelatively large attenuation. Previously published solutions are notable to satisfy attenuation requirements and these solutions are eithernot practically applicable or have only limited applications as forexample in none linear systems, for example frequency modulation forrather limited bandwidths. Therefore it exists a large need for novel,practical solutions that can give repeatable stability combined withrequired gain and signal to noise ratio. There is a need for suchsolutions both for signal repetition with frequency transposing and withsame channel amplification.

SUMMARY OF THE INVENTION

It is one main object of the present invention to provide solutions thatin a low cost and production friendly way secures repeatability, stableoperation and maximum signal dynamics for analogue high frequencyrepeaters in systems specifically for one and two way wire bound digitalcommunication, digital “streaming”, digital “multicast”, digital returnchannel for other systems as in digital point to multiple point and allsimilar systems, but the invention also has important correspondingapplications for wireless transmissions. Besides, one purpose of theinvention is to keep power consumption low with the help of simplicityin design. An additional object of the invention is for it to beinstallation friendly. The object of the invention is also to offerredundancy, improved stability and a wider scope of application for theinventions described in the publications NO20001057, NO20010132,NO20020112, PCT/NO01/00079, PCT/NO03/00004. Further objects of theinvention are achieved by improvement of the stability criteria forrepeaters with gain within the same frequency band both with gains lessthan port isolation and gain larger than port isolation. A similarobject of the invention is achieved with solutions regarding duplexconditions. Still other objects of the invention are achieved withsolutions that reduce mutual interference between repeaters, beatingbetween repeaters and interference from echo or reflections. A furtherobject of the invention is to be able to realise practical solutions fordirectional discrimination and conveying large bandwidths on singleconductors like power lines. One object of the invention is also toallow the solutions by the invention to be utilised in an adaptive waywhere the adaptivity is controlled by local intelligence or by centralintelligence. A further object of the invention is to be able to combineseveral methods of achieving isolation between ports, to reflections andto other repeaters. To a skilled person of the art it will be apparentthat other objects of the invention are obvious.

THE INVENTION

Several objects of the invention are achieved, in a first aspect, by asignal repeater system with analogue amplification as given by theattached independent claim.

Further given objects, in subsequent aspects are achieved with analoguesignal repeater solutions as given by the subsequent attached claims.

Further, advantageous characteristics are given by the attacheddependent claims.

Completely independent of the way in which the first aspect of theinvention is realised in detail the principle of the invention can bedescribed as an analogue repeater system for one- and two way digitaltransmission systems to avoid or reduce satisfactorily echo, reflectionsand mutual interference between repeaters and thereby make efficient useof available channels. This is especially important for modern broadband applications. It is also particularly important in wirelessapplications where the density within many frequency bands is heavy.This may be even more important in cable based systems, especially wherecables with poor high frequency characteristics offer marginal usefulfrequency regions for broad band applications. Power grid cables forlow- and medium voltage are typical examples where there is a need fortwo way communication, metering tasks, smart-house services and otherservices preferably in combination with IP networking and broad bandproducts. Copper networks for telecommunication are contemporaryexamples as well, especially in those parts of the world where theexistence of old copper networks is substantial. The invention can berelated to patent publications NO20001057, NO20010132, NO20020112,PCT/NO01/00079, PCT/NO03/00004 that describe how simple and costeffective frequency transposing can be realised. Here, it is also shownhow frequency shifting between repeaters can be utilised to improvesystem performance with respect to different dynamic properties,robustness against echoes or reflections. These publicationsadditionally show that major advantages in signal dynamics and frequencyband separation within the repeaters themselves can be achieved byintroducing frequency mixing even with the super regenerative repeater.The super regenerative amplifier is both a frequency mixer and anamplifier. It will, without high frequency selectivity both send andreceive within a number of frequency bands with separations equal to thequenching frequency. The number of such bands is given by Q-valuestogether with quench action frequency. A pure, super regenerativerepeater as opposed to a locked oscillator or an oscillating amplifierwill be transparent for all modulation types and for any signal withinthe high frequency pass band of the repeater or amplifier. The inventionmay utilise one or more pilot signals injected at any appropriate pointin a signal cascade and in an appropriate part of the applied frequencyband to facilitate automatic control of gain in each individualrepeater, especially when the high frequency signals contain switchingcharacteristics. The invention makes use of the mentioned factors bybeing able to utilise just two frequency bands for each channel. This isachieved by repeater 1 frequency shifting from frequency f1 to f2. Thenext repeater repeats the signal within the same frequency band f2. Thenext repeater will frequency shift to f1. Further on the sequencerepeats itself. In this way echoes in one repeater from a differentrepeater is avoided because the gain in each individual repeater issubstantially less than the attenuation between three repeaters. Theinvention can perform correspondingly for a second information channel,possibly in a second signal direction for example in an asymmetrical orsymmetrical system or system that requires two channels by utilisingfrequency bands f3 and f4. For asymmetrical systems with low returnbandwidth one frequency may be sufficient if low carrier frequencieswith low attenuation are used. But a second, for instance a higherfrequency can advantageously be applied at a certain physical point toallow signal return to a central unit in case this unit is surrounded byhigh noise level. In this latter case the invention allows frequencyshifting back to the low frequency again if this is desirable forpractical reasons.

When determining the physical distance and position for repeatersgenerally is at liberty as in the cases of open power lines or theirassociated ground lines the invention permits the introduction of addedisolation in the same frequency channel by making every second distancebetween repeaters larger causing a resulting, additional usefulattenuation which is conveniently combined into isolation and requiredsignal dynamics.

One example of repeater is described in patent publications NO20001057,NO20010132, NO20020112, PCT/NO01/00079, PCT/NO03/00004 is a double,super heterodyne repeater where there exists a signal intermediatefrequency which is favourable as a common intermediate frequencytogether with an adapter for a wireless or other high frequency basedmodem as for example a IEEE802.11x node, Docsis node or other type node.The invention facilitates bi-directional mixing of the microwavefrequency of the wireless modem into this intermediate frequency in sucha manner that a modem or a node is connected at any point where there isa repeater of the type referred to and that matches this intermediatefrequency. The invention also describes an adapter solution where inaddition to frequency converting a bypass signal path is arranged usingany kind of stop frequency band arrangement for the frequency convertedfrequency band to achieve acceptable duplex specifications. To improveupon duplex characteristics for high requirements in dynamics theinvention can utilise triple- or higher order super heterodyne, thusallowing receiver and transmitter having different intermediatefrequency to avoid local oscillators reducing dynamics.

Completely independent of the way the invention in it's subsequentaspects is realised in detail the principle of this can be described asa novel method of achieving isolation between input signal and outputsignal for a repeater with antennas or coupling arrangements as well asavoidance of reflections back to the repeater. This is achieved in theinvention using two repeaters that repeats within the same frequencyband but where the two repeaters have different frequency bands for thetwo signal directions. In addition the invention applies oppositeantenna polarisation or coupler polarity or different cable conductorfor the respective signal directions Microwave radio applications canadvantageously apply circular polarisation. The invention is applicableto radio applications where the repeaters should draw low currentslikewise it is suitable for repeater with the Lecher wire principle. Oneexample of use of the invention with the Lecher wire principle is onopen power lines, air mounted ground wires in power transmission linesand two-way microwave signals on such lines and where the purpose is toachieve wide bandwidths. Still another object of the invention is anovel method of achieving directional attenuation and two waytransmission with relatively very large bandwidths across relativelylarge distances on single conductors, especially open power transmissionlines that carry from several kilovolts and up to Megavolt or mastmounted ground lines in connection with such power transmission lineswith the help of compact, practical, analogue repeaters. The inventionis used on a single conductor, for example a power line of the baremetal type, which is thereby used as a waveguide according to the Lecherwire principle. A standard definition of a wave guide is a dielectricmedium constrained or encapsulated by a conductive surface or a materialthat constitutes a dielectric contrast as opposed to a transmission linewhich is likely to have open barriers. A Lecher wire is a combination ofa transmission line, a waveguide and a wandering wave antenna in that ithas an open barrier, for example metal to space. Even though it issimilar to an antenna, it exhibits low radiation losses as long as thewavelength is short. Any metallic conductor without insulation layer orwith thin insulation layer or with insulation layer with a low lossangle may act in a way that resembles a wave guide with very low lossesfor short wavelengths all the way up the millimeter wave regions. Onesuch example of application of the invention using Lecher wire principleis on open power transmission lines and transmission of two waymicrowave signals on such lines and where the object can be to achievevery wide digital bandwidths. With such applications it is importantwith low power consumption because the currents carried in such powerlines have large dynamics and may be down to a few amperes in which caseit is difficult to achieve enough induced energy for powering repeatersrequiring much energy. At higher voltages it may be possible to usecapacitively coupled energy off the power transmission line to power therepeaters. This is also the case when the repeaters are installed on theground wire or ground wires. To facilitate the use of more compact andenergy efficient analogue repeaters it is a requirement that problemsassociated with echo, reflections and directional dampening is solvedwhile efficient excitation of signal power to the signal medium is madepossible at the same time as coupling of signal from the signal mediumfor best signal to noise ratio is possible. An embodiment of theinvention is to regard it as a part radio system and the repeatertechnology of the invention must therefore satisfy some of the moststringent coexisting regulations that exists today and can be expectedin the time to come. Solutions for such repeaters are shown in patentpublications NO20001057, NO20010132, NO20020112, PCT/NO01/00079,PCT/NO03/00004.

The invention in one embodiment has in a given repeater point tworepeaters in the same frequency band where the repeaters satisfy today'scoexistence requirements and where the two repeaters utilise differentfrequency bands for the two signal directions. In addition the inventioncan apply opposite antenna polarisation for the different signal ports.Polarisation may be circular or linear and may be in the form ofantenna; antenna element or probe and a reflector can be used. In oneembodiment the repeaters can be installed on different conductors of apower transmission line to separate the two signal directions. Probingand excitation by the help of the “antennas” is relatively none criticalwhereas the coupling element does not have to be too close to theconductor but in fact may be installed with a practical spacing to theconductor allowing the coupling element to be looking along theconductor line. The coupling elements will look in the respectivedirections from the repeaters. In this way it is possible to installrepeaters that do not make direct galvanic contact with the high voltageconductor.

The invention may correspondingly be made into an embodiment thatutilises frequency-shifting repeaters. Suitable repeaters for thisobject of the invention are also described in the patent publicationsNO20001057, NO20010132, NO20020112, PCT/NO01/00079, PCT/NO03/00004.

An independent embodiment of the invention can be described as a novelmethod to achieve directional dampening, dampening of reflections andtwo way transmission of relatively very large bandwidths on cableinfrastructures, in particular ground buried cables and air mountedcables for low voltage power grids as well as separate conductors withfrom low voltage to several kilovolts using galvanically coupledanalogue repeaters that preferably are placed within junction boxes,transformer sub stations and other types of junctions. In thisinvention, direct coupling through large capacitances or inductances isregarded as galvanic or as direct coupling. The typical embodiment ofthe invention uses differential input or output couplers with respect tocommon mode noise for both immunity and emission characteristics of thesignal system. Embodiments of the invention utilise differential inputand output signal couplers in systems with two conductors and in systemswith more than two conductors as well as in systems that encompassground or neutral conductor. The invention makes use of any given pointon a cable where the conductors are accessible either implicit or bysimple measures taken where between two terminals it may be regarded toexist a two port consisting of three parts, two ports with a transferfunction between them. The transfer function may be given by theconditions each separate conductor possesses and where the point canconsist of one or more junctions, distributed capacitance and variousloss functions. This occurs correspondingly with two conductors or fortwo conductors in a three conductor system and so on further withoutserious effects to the use of two or more conductors in differentialcircuits. The invention makes use of altering the magnetic field aroundthe conductor preferably by the use of toroids that in most cases allowpractical fitting around each conductor. The invention utilisesadvantageously toroids of magnetic material. But the invention alsomakes it possible to use toroids of dielectric materials since materialswith very high dielectric constants have been made commerciallyavailable. Dielectric materials will not have the same drawbacks asmagnetic materials concerning high current levels where none linearityand saturation may cause a problem. The toroid efficiency is increasedby increasing the toroid length or by stacking toroids together. In theinvention a single conductor with a junction may consist of threeseparate toroids, in a three phase cable system with a single phasejunction it may consist of 8 toroids. A two pole of the invention may bedecomposed into separate impedances that can be simulated with computeraid. A single conductor with junction through a typical junction box ina low voltage grid system will typically show 12 dB or more isolationbetween any of the “ports” using galvanic coupling. Without toroids theisolation will be limited to around 6 dB. With regard to a reflectionthis means an isolation of 24 dB and an improvement of 12 dB. Theinvention will show some lower isolation figures with air mountedcables. By introducing additional high frequency impedances between theports, preferably consisting of a capacitor in series with a lowresistance value the figures are usually improved by several dB. With apurely reactive component between the poles of the ports harmfulreflections are a risk.

An independent embodiment of the invention can be described as a novelmethod of achieving directional dampening, dampening of reflections andtwo way transmission of relatively very large bandwidths on cableinfrastructures, in particular ground buried cables and air mountedcables for low voltage and up to a few kilovolts with single conductorswith the help of none galvanic coupled analogue repeaters thatpreferably are installed in junction boxes, transformer sub stations andother types of junctions. Coupling through inductive loops orcapacitances of low values or combinations of these are regarded as nonegalvanic or none direct coupling in the invention. A combination ofgalvanic and none galvanic coupling with repeaters is regarded as partof this novel aspect of the invention. Differential input and outputcoupling is utilised in the invention in most cases with respect tocommon mode noise related to immunity and emission characteristics ofthe signal system. The principle of the invention with galvanic couplingis a coupling conductor loop where one part of the loop is carried in acertain length very close to the cable conductor to which the couplingis intended. If the cable conductor and the nearby loop conductor arecarried through a toroid of magnetic or dielectric material, thecoupling efficiency is increased. The coupling arrangement of theinvention may be made more efficient by making the respective loopconductor into a few turns through the toroid. Still more improvement ofthe coupling in the invention results by stacking a number of toroidsthat the cable conductor and the loop conductor pass through. For higherfrequencies and when less attenuation between cable terminals isrequired the magnetic or dielectric material may take a different formor may be omitted completely. Using these various methods in theinvention allow sufficient coupling for achieving coupling efficiencyequivalent to galvanic coupling even down to frequencies of a fewMegahertz. Differential coupling using two cable conductors is achievedwith corresponding arrangement on the second cable conductor andallowing the loop conductor to be routed through both toroids. Multiplephase connection embodiments are realised in a corresponding manner. Onesimple form of matching may be achieved with a resistance in seriesinside the coupling loop. The invention can make use of any phasecombination and this function may be programmable or adaptive forexample using a simple circuit with a selector. In a couplingarrangement using two cable junctions two separate coupling loops willtypically offer better than 20 dB isolation between the coupling loops,in optimised cases, for example using additional termination impedance,better than 30 dB isolation between the coupling loops may be achievedin the invention across a wide frequency region from high frequency towell into the VHF frequency region. The invention gives isolationbetween cable junctions on high frequency of 12 to 20 dB depending onthe impedance in the middle of the circuit. Correspondingly theinvention offers isolation between all coupling loops when there aremore than two such, for example as with three cable junctions usingthree none galvanic couplings. For three such loops the isolation isstill better than 20 dB between any of the three loops or ports. Theinvention facilitates combination of galvanic and none galvaniccoupling, for example by the use of galvanic coupling for one signaldirection carrying the lower frequency region where none galvaniccoupling is less efficient.

SHORT DESCRIPTION OF FIGURES

The present invention is described in more detail in the following withexamples and references to the appended drawings, where

FIG. 1 shows with block diagram how repeater frequencies are arranged inrelation to dampening between repeaters and signal directions.

FIG. 2 shows an example of an analogue repeater employing the doublesuper heterodyne principle and one intermediate frequency thatadvantageously has a centre frequency of several hundred Megahertz.

FIG. 3 shows how an adapter can be arranged between a modem and arepeater using intermediate frequency as shown in FIG. 2.

FIG. 4 shows how an adapter can be arranged between a signal point and amodem for independent downstream and upstream channels.

FIG. 5 shows how bi-directional, often one port repeaters can bearranged so that unwanted coupling and reflections are reduced by theaid of unidirectional amplifiers and inverted antenna polarisation.

FIG. 6 shows how in the invention any point on a cable where conductorsare accessible either implicit or through simple measures between twodifferent junctions can be regarded as consisting of a two port made upof three parts.

FIG. 7 shows that the invention makes use of altering the magnetic fieldaround the conductor preferably by installing toroids on each individualconductor.

FIG. 8 shows that a two pole in accordance with the invention may bedecomposed into different impedances. A single conductor with a junctionin a typical junction box is shown with respect to dampening.

FIG. 9 shows repeaters for two way transmission of relatively very largebandwidths across relatively long distances on single conductors, mainlypower transmission lines.

FIG. 10 shows the principle of the invention for none galvanic coupling.

FIG. 11 shows differential coupling with two cable conductors.

FIG. 12 shows how any combination of phase can be programmable oradaptive for example through a simple circuit using a selector.

FIG. 13 shows a coupler arrangement with two cable junctions with highattenuation between the coupler loops. Correspondingly it shows anarrangement that exhibits equally large attenuation between any of thethree coupler loops.

DETAILED DESCRIPTION

FIG. 1 illustrates how the invention in a repeater system 1 or arepeater cascade 1 makes use of frequency transposing repeaters whereisolation against echo between repeaters is made redundant by the use ofthree frequency bands, f1, f2, f2 for each information channel, possiblyeach signal direction in use. The figure shows in more detail how theinvention makes use of a repeater cascade 1 with the help of frequencytransposing repeaters 6, 8 in combination with repeaters that amplifieswithin the same channel 7, 9 by applying only two frequency bands, f1and f2 for on and the same information channel. This is achieved in asymmetrical system by repeater 6 frequency shifting from frequency f1 tof2. The nest repeater 7 repeats the signal within the same frequencyband, f2. The next repeater 8 repeats by frequency shifting to f1.Further on the sequence is repeated starting with the subsequentattenuation 5 and repeater 9. In this way echo for example into onerepeater 6 from a different repeater 8 is avoided because the gain ineach individual repeater 6, 7, 8 is substantially lower than theattenuation 3, 4 between three repeaters. This results in optimal signaldynamics. Correspondingly the invention facilitates the same method tobe used in the opposite direction 16 in an asymmetrical or symmetricalsystem or system that needs two information channels by utilisingrepeaters 10-13 for the frequency bands f3 and f4. One or more pilotsignals 16 can be inserted in one or more points 17 in the signalcascade 2, 14 to ease automatic adjustments of the gain in each repeater6-9, 10-13. When the liberty to determine freely the physical distanceand position for repeaters is available as is the case on open powertransmission lines or ground lines in such systems, the invention allowsthe insertion of an additional 20 dB isolation in the same frequencychannel by making every other distance between the repeaters larger toresult in approximately 20 dB additional attenuation. About 20 dBreduction of transmission power is allowable without causing undesiredeffects, therefore the invention can be realised in such a way thatevery other repeater has an output level of for example 0 dBm whilecorrespondingly every other repeater has −10 dBm. Alternatively, thedifference in output power may be adjusted automatically with AGCarrangements possibly by the help pilot signals between the repeaters.

In FIG. 2 is shown an example of repeater as described in patentpublications NO20001057, NO20010132, NO20020112, PCT/NO01/00079,PCT/NO03/00004 which is a double or multiple super heterodyne repeater38 where in the invention it is arranged with a signal intermediatefrequency 33 being suitable for adaptation to an analogue repeater 38using for example a common intermediate frequency 25, 31 with an adapter36 for wireless modem or other commercially available modem or networknode 36 which may be a IEEE802.11x node or modem 36 or Docsis node ormodem 36. The invention may also be used for symmetrical modems that canbe interconnected back to back almost anywhere in the system andindependently of which modulation or protocol the system is using insuch a way that the invention facilitates the use of differing,standardised modulation types and protocols within one and the samesystem, for example to achieve adaptive qualities and longer range in alow cost manner in parts of the system, possibly with the penalty ofreduced bandwidth in parts of the system. If such modems use base band amodulator and demodulator is required, preferably of the I/O type, andinserted in connection with the adapter 36 if higher frequency bands areto be used for the transmission between the back to back modems. Suchtypical modems are DSL modems, for example HDSL The invention alsoencompass viable corresponding arrangements using super regenerativerepeater 38 which eventually would use intermediate frequency 25, 31with the help of the super heterodyne principle. The repeater may beinterconnected in the cascade as a two port through circuits 21, 26 oras a one port with the aid of the circuit 39. In FIG. 3 it is shown howthe invention facilitates bi-directional frequency mixing in an adapter41 with signal frequency 43 that may be a microwave signal frequency 43of a commercially available type network node 42, which may convenientlybe a wireless modem 42, to this intermediate frequency whereby such amodem 42 or a node 42 or PC adapter 42 can be connected at any point 51where a repeater 38 of the type described in FIG. 2 is present and whichcontain frequency corresponding to intermediate frequency 45, 49, 50.The repeater 41 is connected at any point 51 in an analogue signalcascade 52. Bi-directional frequency conversion can be applied using abi-directional frequency converter 44 such as a diode ring mixer, stillsimpler bi-directional diode mixers or as two separate frequency mixers.Additionally, gain 48, 49 can be included in the invention. If the node42 does not have a removable antenna 53, the connection between adapter41 and node 42 can be satisfied using a loose coupling 53 to the antennacorresponding to signal point 53.

In FIG. 4 one arrangement of the invention is shown with an adaptersolution 61 corresponding to the one in FIG. 2. Here it is shown how theinvention in addition to frequency converter 64 using level adaptingcharacteristics facilitates the arrangement of a bypass signal path 63,65-69, with or without frequency conversion, for return signals 63 usinga stop filter 69 for the available frequency band in the forwarddirection 62 to achieve acceptable duplex characteristics.

In FIG. 5 a novel method of combining 70 bi-directional gain withisolation between input signal and output signal 73-76 is accomplishedfor a repeater 70 with antennas 71, 72, antenna like couplers 71, 72 orother types of couplers 71, 72 as well as avoidance of reflections backto the repeaters 82, 83. This is achieved in the invention using twofrequency bands with two repeaters 82, 83 that repeats within the samefrequency bands 74-76, 73-75 but where the two bi-directional,conveniently one-port repeaters 82, 83 have differing frequency bandsfor the two signal directions 74-76, 73-75. In addition, the inventioncan utilise separate amplifiers 77-80, 78-79 for added isolation forinput and output signals 76-73, 75-74 and opposite antenna polarisation,differing coupler polarity or differing cable phases for the differingsignal directions 73-74, 75-76 or for the differing ports 74-76, 72-75.For radio or applications similar to radio, circular polarisation mayconveniently be used. The repeater arrangement can carry built in radiointerface 81 of any type preferably one with low current draws and inwhich analogue technology described in patent publications NO20001057,NO20010132, NO20020112, PCT/NO01/00079, PCT/NO03/00004 can be applied.The radio interface can be two-way and can be used as a none galvaniccoupling to the outside world which typically will be another radio unitat close range. The invention is suitable for radio applications wherethe repeaters 70 is to consume little energy, similarly it is suitablefor repeater 70 on conductors that are brought to act according to theLecher wire principle.

FIG. 6 shows that the invention can make use of the fact that anyphysical point on a cable where conductors are accessible eitherimplicit or through simple measures between two junctions can be viewedas consisting of a two port 90 consisting of three parts 91, 92, 93, twoports 98 and 97, 94 and 95 including a transfer function 92 betweenthem. The transfer function 92 can be given by the properties of eachconductor 114 where the point 110 can consist of one or more junctions,stray capacitance, inductance and various loss functions.Correspondingly is provided for two conductors 109, 101, 102 or for twoconductors 121, 122, 123 in a three conductor system 120 and so on andwithout significant affect on the use of two or more conductors indifferential couplings.

FIG. 7 shows that the invention makes use of changing the magnetic fieldaround the conductor preferably by toroids 140, in most cases beingpracticably installable 141, 142, 143 on each conductor 154, 155, 156.The invention can advantageously make use of toroids of magneticmaterials. But it is also possible to use toroids of dielectric materialsince materials with very high dielectric constants have becomecommercially available. With respect to toroids the effect is increasedby increasing the toroid length or by stacking a number of toroids. Inthe invention each conductor 150 with a junction will consist of threeseparated toroids 154-156, for a three phase cable system 160 with a onephase junction 163 the invention will typically consist of 8 toroids.

FIG. 8 shows that a two pole according to the invention may bedecomposed into various impedances 170, Z1-Z9 that may be simulatedusing computer. A single conductor 180 with a junction though a typicaljunction box within a power grid system will typically exhibit 12 dB ormore attenuation between any of the “ports” using galvanic coupling.Without toroids the attenuation will be limited to around 6 dB. For areflection this means a dampening of 24 dB and an improvement of 12 dB.The invention will exhibit somewhat lower attenuation with air mountedcables. By inserting an extra high frequency impedance in Z9, 170,between the ports, preferably consisting of a capacitor in series with alow resistance value, these figures are usually improved by several dB.

FIG. 9 shows repeaters 195, 198, 201, 218, 219, 235 preferably for twoway transmission of relatively large bandwidths across relatively longranges on single conductors 191-193, 211-213, 232 especially on openpower lines that carry from a few kilovolts and up to Megavolts or mastmounted ground lines in connection with such power lines using compact,practical analogue repeaters. This then concerns also when the repeatersare installed on the ground line 241 or ground lines 241. The inventionin one realisation can in a given repeater point 190, 210, 230 tworepeaters in each unit 195, 198, 201, 218, 219, 235 that repeats withinthe same frequency band where the repeaters within each unit 195, 198,201, 218, 219, 235 satisfies today's coexistence requirements and wherethe two repeaters utilise differing frequency bands for the two signaldirections 203, 204.

In addition the invention can apply opposite antenna polarisation194-196, 197-199, 200-202 for the differing signal ports. Thepolarisation can be circular or linear and be in the form of an antenna194, 196, 197, 199, 200, 202, antenna element 194, 196, 197, 199, 200,202 or probe 194, 196, 197, 199, 200, 202 and a reflector can be used.In one embodiment of the invention the repeaters can be installed ondifferent conductors 211, 213 in a mast power line system to betterseparate the two signal directions. Correspondingly one embodiment ofthe invention can be arranged to utilise frequency shifting repeaters195, 198, 201, 218, 219, 235. Suitable repeaters for the purpose is alsodescribed in patent publications NO20001057, NO20010132, NO20020112,PCT/NO01/00079, PCT/NO03/00004.

FIG. 10 shows that the principle 250 of none galvanic coupling of theinvention is a coupler conductor loop 252 where the one part of the loopis lead at a certain length very close to the cable conductor 251 towhich coupling is intended. If the cable conductor and the closest loopconductor is carried through a toroid 253 of magnetic or dielectricmaterial the coupling is increased. The circuit arrangement 250 of theinvention can be made still more efficient by the referenced loopconductor 252 being wound as a few turns around the toroid 253. Stillmore improvement of the coupling 260 results when in the invention anumber of toroids 263, 264 are stacked and where the cable conductor 261and the loop conductor 262 are passed through the stacked toroids.

FIG. 11 shows that differential coupling in the invention using twocable conductors is achieved by employing a corresponding arrangement onthe other cable conductor and making the loop conductor 314 pass throughboth toroids 316, 317 in the same manner. Multiple phase couplings canbe realised correspondingly. A simple form of matching is achieved usinga resistance 318 in series with the coupler loop 313.

FIG. 12 shows that the invention can make use of any phase combination330 and this may be programmable or adaptive for example by using asimple circuit with a switch 334 for example by using a common couplerloop conductor 335.

FIG. 13 shows a coupler arrangement 360 with two cable junctions 361,362 with two separate coupler loops 363, 365 with increased mutualattenuation between coupler loops 363, 365 that can be optimised usingan additional load impedance inserted in the middle of the circuit inaddition to the implicit 371. Correspondingly 390 the invention givesisolation between all coupler loops 363, 365, 381 when there are morethan two such coupler loops, for example as in the case of three cablejunctions 361, 362, 380 using three none galvanic couplers. Theinvention makes it possible to combine galvanic and none galvaniccoupling, for example by using galvanic coupling for one signaldirection carrying the lowest frequency content where none galvaniccoupling is less efficient and where the galvanic coupling can be madeon the terminals 361, 362.

1. Analog signal repeater system used in a power grid and distributionsystem where repeaters with signal gains are applied to extend radiofrequency transmission range across a number of termination cablejunction arrangements in different physical positions with cablesinterconnecting them for stable utilization of repeater gains and forbandwidth improvement as a function of transmission range, comprising:the signal repeater system with repeaters connected through differentialsignal couplers consisting of at least one signal coupler arrangementand at least two series impedances and at least one shunt impedance;whereby at least one signal transmission range is facilitated to acceptradio frequency gains at the junctions, wherein at least two of theelectrically accessible junctions include at least one repeater at eachof said junctions, where signal couplers on cables of the junctionsfacilitate signal bypassing of the junctions and where the combinationof transfer losses and inserted dampening in each of the junctionsbetween signal couplers at each of the junctions increase signalisolation between ports of the repeaters at the junctions to mitigateproblems from undesired signal coupling between ports of the repeaters.2. Analog signal repeater system according to claim 1, furthercomprising the system to be using one of said repeaters for eachtransmission direction at each of said junctions and where saidrepeaters are using at least different frequency bands for saidtransmission directions in each repeater point to achieve duplex andsignal transmission in more than one direction across said signaltransmission distance enabled by the signal dampening in the junctions.3. Analog signal repeater system according to claim 1, wherein saidfrequency bands being used by said repeaters to employ frequencyconversion enabled by the signal dampening in the junctions.
 4. Analogsignal repeater system according to claim 1, further comprising anadapter connected to at least one of said repeaters allowing equipmentwith standardized modulation and protocol that include duplex systemstandards as in Docsis cable modem standards enabled by the signaldampening in the junctions.
 5. Analog signal repeater system accordingto claim 1, wherein the repeaters at the junctions are using twofrequency bands using two of said repeaters in at least one repeaterpoint where said repeaters each repeat signals on the same frequency inone of said frequency bands to provide full duplex transmission enabledby the signal dampening in the junctions.
 6. Analog signal repeatersystem according to claim 1, further comprising at least one of saidrepeaters with said two way transmission to be interfaced to two-waywireless communication device enabled by the signal gain at thejunctions.
 7. Analog signal repeater system according to claim 1,wherein the said isolation between ports in electrically accessiblephysical points consisting of conductor junctions is increased usingtoroids with magnetic material on at least two conductors whiledifferential signal couplers are connected galvanically throughcapacitors to at least two conductors on the cable side and while atleast one capacitor differentially provides a high frequency lowimpedance shunt impedance for at least two conductors on the junctionside.
 8. Analog signal repeater system according to claim 1, wherein atleast one junction is utilizing a single conductor for signaltransmission in at least one direction between at least two of saidrepeaters enabled by the signal dampening in the junctions.
 9. Analogsignal repeater system according to claim 1, wherein at least onejunction is using at least one conductor for additional signal bypassenabled by the signal dampening in the junctions.
 10. Analog signalrepeater system according to claim 1, wherein the said isolation betweenports in electrically accessible physical points consisting of conductorjunctions is increased using toroids with magnetic material on at leasttwo conductors while differential signal couplers are connected to awire looping through said toroids on at least said two conductors on thecable side and while at least one capacitor differentially provides ahigh frequency low shunt impedance for at least two conductors on thejunction side.